title: First-principles calculations of Zn-K XANES in Ca-deficient hydroxyapatite.
abstract: The local environment of substitutional Zn(2+) in Ca-deficient hydroxyapatite (HAp) was investigated using experimental and theoretical analyses of the x-ray absorption near edge structure (XANES). For Zn-K XANES calculations, two situations of Zn(2+) were considered. One was Zn(2+) substituted for Ca sites in perfect HAp, and the other was a Ca-deficient HAp model of substitutional Zn(2+) associated with a Ca(2+) vacancy charge compensated by two protons. The model of Zn(2+) in perfect HAp did not reproduce the experimental Zn-K XANES spectrum. In contrast, the Ca-deficient HAp model agreed well with the experimental spectrum. This indicates that substitutional Zn(2+) in Ca-deficient HAp is associated with the Ca(2+) vacancy complex in HAp.
authors.affiliation: Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan. hidenobu.murata@hw7.ecs.kyoto-u.ac.jp
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Murata
authors.forename: Kazuki
authors.initials: K
authors.lastname: Shitara
authors.forename: Isao
authors.initials: I
authors.lastname: Tanaka
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakahira
authors.forename: Teruyasu
authors.initials: T
authors.lastname: Mizoguchi
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Matsunaga
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D001703:Biophysics / Q000379:methods; D002118:Calcium / Q000737:chemistry*; D003460:Crystallization; D017886:Durapatite / Q000737:chemistry*; D004581:Electronics; D006801:Humans; D008670:Metals / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry; D010825:Physics / Q000379:methods; D011188:Potassium / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014732:Vibration; D014965:X-Rays; D015032:Zinc / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D008670:Metals; D010087:Oxides; D017886:Durapatite; D015032:Zinc; D011188:Potassium; D002118:Calcium